The present invention relates to a process for obtaining bimaterial parts by casting an alloy around insert coated with a metal film.
The invention relates, more particularly, to the parts formed from an insert of aluminum or of another metal such as iron or copper, which is at least partly integrated into an aluminum alloy matrix, during a casting operation.
This particular structure is used, for example, for the manufacture of car parts such as engine cylinder heads, in order to try to locally modify their properties, and for inserting pipes into aeronautical molded parts.
In fact, it is known that such parts are locally subjected to stresses during use, in particular thermal stress, and that to avoid certain effects detrimental to their behavior, inserts having properties which better satisfy the stresses than the base material, are usually embedded in the parts.
However, it has been noted that the manufacture of these bimaterial parts was problematical, particularly in respect of the bond between the insert and the metal cast around it.
In fact, on the one hand, adherence between the constituent parts is not always as it should be, and as a result the mechanical properties or physical properties such as heat conductivity are inadequate; on the other hand, since the casting is made with the metal in the molten state by filling a mold in which the insert has been placed, if the metal forming the insert has a fusion temperature which is less than, or close to, that of the casting metal, the insert becomes deformed, and this is detrimental to correct localization thereof.